CInt FFI exports do not use C int in _stub.h header file

Ideally if I have a FFI export like this:

foreign export ccall foo :: CInt -> CInt

Then the _stub.h file should look like:

#ifdef __cplusplus
extern "C" {
#endif
extern int foo(int a1);
#ifdef __cplusplus
}
#endif

But it actually looks like:

#include "HsFFI.h"
#ifdef __cplusplus
extern "C" {
#endif
extern HsInt32 foo(HsInt32 a1);
#ifdef __cplusplus
}
#endif

So what am I complaining about? Well, I specified an FFI export mentioning only C types but the header file uses HsInt32. I'd prefer an actual C int. I also do not want to #include "HsFFI.h" because then when using gcc to compile C code that uses this C function I have to know the full path to ghc's include dir so that gcc can find HsFFI.h.

The point here is about exporting C functions and trying to integrate into some bigger build system that will be using gcc not ghc to compile C code and link the system together.

I realise this isn't trivial to fix, because GHC defines things like CInt as newtypes for primitive types of known widths (like Int32). However, perhaps there should be a known mapping, even though within the Haskell world CInt is just a newtype. The set of FFI types is already hard-wired into the compiler (with some rules to allow newtype unwrapping etc) so why not extend that hard-wired knowledge to include the real C type (not just the ABI width). This only needs to be used when generating the export header files. An extra bit in the mapping can indicate if it's a C primitive type or if the export header file has to #include "HsFFI.h".

This ticket is related to #2926 and the solution is almost certainly the same, but the motivation for this problem is slightly different.

Trac metadata

Trac field	Value
Version	6.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (FFI)
Test case
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